22
.
USE OF A PORTABLE WHOLE-BODY COUNTER
residual radionuclides not presentin sufficient
quantity to reveal themselves via their photopeaks. The adult groups all had approximately
the same level of residual activity, while the
juveniles had apparent values of 25-50 per cent
of the levels of the adults. These lower values
may be due, in part, to the use of the standard
man phantom in calibration of the various
radionuclides in the juveniles. The oversubtracting of the low energy end ofthe calibration
spectra would give an apparent lower residual
value for the juveniles. The residual activity
values in the adult groups wereatleast 10 times
the mean observed in the U.S. medical team.
Unfortunately whole-body counting techniques
have not been developed for external beta
counting of the very importantfission product
Sr®°, Its levels can only be estimated from data
obtained by radiochemical analysis of urine.
Undoubtedly the bremsstrahlung resulting from
the Sr®° body burdens in the Marshallese
contributes to the residual activity noted above.
A study of the levels of body burdens of the
several y-emitting radionuclides in the Marshallese people indicates how the fission products
the best solution to the problem of setting up a
satisfactory counting geometry forfield use, as it
enables calibration measurements to be checked
at later times in the “home”laboratory.
- The whole-body y-spectrometer can be
valuable in the field, not only to surveysituations in which populations are contaminated
with radionuclides, but as a clinical research
tool.(8) It is possible, and may be desirable, to
carry out in the field demographic studies with
the use of radioactive tracers, and it is also
possible to carry out such clinical studies as the
investigation of metabolic and nutritional
diseases, which may have their origin in the
particular local environment.
Thus the portable whole-body spectrometer
is an instrument with considerable application
in health physics and clinical research problems.
GONCLUSION
The usefulness of a portable whole-body y-
spectrometer in the assay of the body burdens of
mixed fission products and induced activities is
illustrated by the 1961 field study of the internal
contamination in a population of Marshallese
move through the environment and accumulate people at Rongelap Atoll. The apparatus and
in man. Further, the biological turnoverrate of the techniques of measurement, automatic
these radionuclides in human beings can be data-handling and computeranalysis of complex
estimated. The survey made with the portable spectra are described, Theresults of the spectral
whole-body counter has veen invaluable in analyses are presented and compared with a
monitoring the levels of internal contamination comtrol group, and with the previous values
of y-emitters in this population. The experience obtained.
gained in this study should be of value in future
In addition to its application in the detersurveys among other populations.
mination ofbody burdensofradioactive isotopes
No difficulty was encountered in setting up in populations exposed to fission products,
the shielding for the BNL portable counter as mumerous clinical applications of the wholeequipment for moving it intact was readily body y-spectrometer may be made. Studies of
available. Although it was not necessary to large scale health problems, such as epidemics
dismantle the shielding between surveys, it by meansof radioactive tracers and whole-body
would not have been difficult to do so. How- counting, offer a new approach to a numberof
ever, because of the weight and bulk of the old problems. By meansof the portable wholeshielding, thought has been given to developing body counter, these studies may be carried out
other types of shielding for use in the field, anywhere in the world.
particularly for use in places where weight
might give rise to transportation difficulties.
REFERENCES
Materials other than steel and in smaller units of
L. E. C. Anperson, R. L. Scuucu, W. R. FisHer
weight might possibly be used. The shipment
and W. Lancuam, Science 125, 1273 (1957).
and operation of the electronic facilities present
2. €. E. MILier and L. D. Marineut, Science 124,
no particular problem.
Once a satisfactory
counting geometry has been worked out at the
“home”? installation, its duplication provides
122 (1956).
3. C.E. Miter, Measurements on Some Residents of the
Marshall Islands. ANL. Report 5755, p. 56 (1957).